Ideally you should create a certificate request and provide it to the CA for obtaining a corresponding certificate. Then import the respective certificate into the wallet. It appears as if your certificate request is not matching with the user Certificate. Please confirm.

Please make sure to follow the suggested steps only for host certificate. The Trading partner certificate is not part of the wallet , instead it should be browsed while modelling it and will be stored in the repository. I guess you are trying to import TP certificate also into the wallet.